Correct installation of vapor barriers

I live in New England and
am confused as to the correct installation of vapor barriers. I see
them on the outside of some houses and on the inside walls in others.
My next project will be finishing my basement. Does the barrier
go against the concrete wall or does it go on the studs just behind
the sheetrock?

1. Where outside humidity is not a problem,
the vapor barrier is installed on the warm side of the wall. During
the winter, water vapor is blocked from penetrating the insulation
and condensing on a cold outside surface.

2. Where outside humidity is high in the
summer and air conditioning is used, a vapor barrier is recommended
on the exterior wall (warm side). During the winter, the interior
vapor barrier prevents water vapor from penetrating the insulation
and condensing on a cold surface. During the summer, the exterior
vapor barrier can prevent water vapor from penetrating the insulation
from the outside and condensing on a cold air conditioned surface
on the inside of the wall.

For your situation in the basement,
place the vapor barrier on the interior wall over the studs just
behind the wallboard. However, when installing the insulation, be
sure to not use a Kraft face insulation. Any moisture that may get
trapped will create mold and mildew on the face of the insulation.

You would be better off installing faceless insulation or foil back
instead of the vapor barrier. Or you could install an encapsulated
insulation that's poly-wrapped. This is twice as resistant to moisture
penetration than Kraft facing. It serves as a vapor barrier; however,
in order for it to work, you need to face staple, i.e., staple the
tabs across the face of the studs, the same as you would for the
foil face. Check with your local building department to see which
is better for your environment.

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